The present invention relates to a label which can be permanently adhered to a rubber tire such as an automobile tire or an airplane tire and more particularly to an indication label material on which an indication such as a bar code can be printed by using a thermal transfer printer and a label on which the indication has been printed.
In a process for manufacturing a vehicle rubber tire such as an automobile tire, an indication label is attached to each unvulcanized tire for assisting in management of the quality. After the indication label indicating, for example a production lot, stuck thereto is attached to an unvulcanized raw tire, the raw tire is vulcanized in a mold. Accordingly, the indication label to be used for such a purpose must firmly adhere to the rubber tire and not separate therefrom. In addition, the label must maintain its characteristic as a clear indication without being influenced by heat and pressure applied thereto during the process of vulcanizing the raw tire in the mold.
In order to comply with such a need, various kinds of indication labels for adhesion to a rubber tire have been proposed as disclosed in Japanese Utility Model Publication No. 54-16636, Japanese Patent Publication No. 53-29595, Japanese Utility Model Publication No. 62-3814, and Japanese Patent Publication No. 63-42263.
However, in each of these conventional indication labels for adhesion to a rubber tire, a plastic film such as a transparent polyester film is laminated on a printing layer for intercepting the influence of heat or pressure applied thereto when vulcanizing the raw tire in the mold. Therefore, an indication label must be created under specific conditions before adhering the label by printing an indication, laminating a plastics film over the indication for the protection of the printing and finally die-cutting the labels.
In recent years, management labels having a bar code printed thereon have been used in various fields of industry. It is well known that the most effective way for using these management labels is to apply an indication on a pre-die-cut label during manufacturing. Normally, a thermal transfer printer is used to print the indication on the label.
There is a disadvantage in utilizing the above described method of printing indications during the process of manufacturing of the rubber tire. That is, in printing the indication during the manufacturing process using a thermal transfer printer, thermal transfer ink does not have heat-resistant properties. Thus, a thermal transfer ink layer melts in the process of vulcanizing the raw tire. When the melted ink contacts the metal surface of the vulcanizing mold, the ink tends to be transferred thereto. As a result, the density of the printed image of the indication is reduced; the printed indication is destroyed; or the ink transferred to the metal surface of the vulcanizing mold is re-transferred to the label thereby contaminating the indication and preventing the bar code from being correctly read. In order to protect the printing layer, a plastics film must be manually applied over the pre-die-cut label. However, such application is believed to be disadvantageous as part of the manufacturing process since it increases the time and cost associated with making the tire.